Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
import sys
import queue

H,W = map(int,input().split())
white = 0
maze = []
for y in range(H):
	li = list(input())
	white += li.count('.')
	maze.append(li)

def check(x,y,n):
	if 0 <= x < W and 0 <= y < H:
		if x == W-1 and y == H-1:
			print (white - n - 1)
			sys.exit()
		elif maze[y][x] == '.':
			maze[y][x] = n
			q.put([x-1,y,n+1])
			q.put([x+1,y,n+1])
			q.put([x,y-1,n+1])
			q.put([x,y+1,n+1])
		else:
			return
	else:
		return

q = queue.Queue()
q.put([0,0,0])
while not q.empty():
	x,y,n = q.get()
	check(x,y,n)

print(-1)